Measure and cut two 2-by-4s into 4-foot lengths. These four pieces will become the legs for the sawhorse.
Measure and cut the remaining 2-by-4 into two 4-foot lengths. One of these lengths is used for the top crosspiece that connects the two sets of legs. The second 4-foot section can be used as an optional cap for the crosspiece.
Insert one 4-foot leg section into each of the bracket's leg openings.
Secure the leg sections into the bracket with drywall screws. Use a drill with a driver bit to insert a screw into each of the predrilled holes in the bracket.
Repeat Steps 3 and 4 for the remaining bracket.
Place the crosspiece into the jaws on the brackets. The crosspiece should extend 6 inches past the outside of each bracket.
Spread the legs attached to the brackets to lock the crosspiece in place. When you are finished working on the sawhorses, simply push the legs back together, remove the crosspiece and store the disassembled sections in a convenient location.